Field of the Invention
The present invention relates to a copier, a printer, an image forming apparatus, such as an MFP (Multi-Functional Peripheral) incorporating a copier and a printer, etc., and an image forming system in which an image forming apparatus and a post processing apparatus and/or the like are coupled to each other.
Description of Related Art
Generally speaking, an image forming apparatus, such as a copier, a printer, etc., is provided with a plurality of paper sheet feeding trays, which accommodate plural kinds of paper sheets respectively therein, in order to cope with various kinds of printing conditions. Further, in order to individually cope with a huge variety of printed paper sheets, sometimes, a single or a plurality of post processing apparatus that applies various kinds of processing to paper sheets on which images are already formed, may be cascaded to the image forming apparatus as the post processing stage thereof, so as to configure a structural configuration of an image forming system.
Further, in such a case where various kinds of post processing apparatuses or the like are coupled to the image forming apparatus as above-mentioned, sometimes, a plurality of ejecting trays, respectively corresponding to the various kinds of post processing, may be provided in the image forming system. In this connection, according to the conventionally existing technology, in case that a paper jam failure has occurred at a certain position within the image forming system, after the operation of the image forming system has been made to halt, a single or a plurality of jam-subsequent paper sheets is collected onto a specific tray to make them eject from the image forming system as a purge processing.
Incidentally, with respect to operations for handling the jam-subsequent paper sheets, various kinds of Patent Documents, including Japanese Patent Application Laid-Open Publication No. 2008-052125 (hereinafter, referred to as Document 1), Japanese Patent Application Laid-Open Publication No. 2006-343727 (hereinafter, referred to as Document 2), Japanese Patent Application Laid-Open Publication No. 2003-280304 (hereinafter, referred to as Document 3), Japanese Patent Application Laid-Open Publication No. Tokkaihei 11-292389 (hereinafter, referred to as Document 4), Japanese Patent Application Laid-Open Publication No. Tokkaihei 07-120984 (hereinafter, referred to as Document 5), etc., set forth various kinds of technologies, respectively.
According to Document 1 above-cited, at the time when a paper jam has occurred, with respect to a paper sheet that is located upstream from the jam-causing paper sheet and can be conveyed to any one of the ejecting destinations, the conveying operation thereof is to be continued, so as to eject the paper sheet therefrom as the pre-purge processing. On the other hand, with respect to another paper sheet that cannot be ejected, the purge processing is applied thereto, after the jam-causing paper sheet (defined as a paper sheet at which the concerned paper jam has occurred) has been removed.
According to Document 2 above-cited, at the time when a paper jam has occurred, instead of halting the operations for conveying all of the paper sheets currently residing within the apparatus as a whole, only the operation for conveying the jam-causing paper sheet is halted. Then, the operation for conveying a paper sheet, other than the jam-causing paper sheet and remaining within the apparatus, is continued, so as to eject the paper sheet as the pre-purge processing.
According to Document 3 above-cited, at the time when a paper jam has occurred within the image forming apparatus main-body, provided that a jam occurrence position is located upstream from the insertion merging point of the insertion paper sheet, the current operation of the image forming apparatus is deactivated, immediately after the insertion paper sheet has been swept out.
According to Document 4 above-cited, at the time when a paper jam has occurred at a certain position within the image forming system, jam-subsequent paper sheets currently remaining within the image forming system are collected onto a specific one of the ejecting tray, which is selectable by the user, to eject them therefrom.
According to Document 5 above-cited, at the time when a paper jam has occurred at the reciprocal conveyance duplex unit, a paper sheet on both sides of which duplex images are already formed is to be ejected, while another paper sheet on one side of which an image is already formed is conveyed to the standby position (reverse position) located upstream from the jam-causing paper sheet.
In this connection, hereinafter in an image forming apparatus or an image forming system, such a state that an operation for conveying a paper sheet is disabled due to a paper jam currently occurring at any one of the various conveyance sections, is defined as a primary abnormal state. Further, in the primary abnormal state above-defined, the image forming apparatus or the image forming system recognizes an occurrence of a primary paper jam, and the control section thereof conducts controlling operations for halting the conveyance operation of the paper sheet concerned.
Further, hereinafter in an image forming apparatus or an image forming system, such an abnormal state, in which a certain negative influence would be possibly given to the image quality, such as an inclination of an image formed on the paper sheet, a dropout of an image to be formed on the paper sheet, or the like, due to an abnormality of the paper sheet conveyance operation, such as the inclined conveyance, the leaning conveyance to one side, the duplicate conveyance, etc., is defined as a secondary abnormal state.
In the meantime, in a case where a paper jam has occurred at a jam-causing paper sheet, and the pre-purge processing is to be applied to a jam-subsequent paper sheet located upstream from the jam-causing paper sheet, sometimes, another paper jam may occur at the jam-subsequent paper sheet in midcourse of applying the pre-purge processing thereto.
For instance, at the time when a paper jam has occurred due to the fact that a concerned paper sheet is jammed with a pair of conveyance rollers located at a certain position, jam-subsequent paper sheets reside at various kinds of positions, such as a position in the vicinity of a paper sheet feeding section, a position in the vicinity of a toner image transferring point, etc., which is located upstream from the position of the jam-causing paper sheet.
Accordingly, in the above-mentioned case, owing to various kinds of adverse factors, including a leaning or inclination of a paper sheet residing in the vicinity of a toner image transferring point, a duplicate conveyance performed by the paper sheet feeding section, a delay of timing for feeding a paper sheet residing at a pair of paper sheet feeding rollers or a resist roller, etc., even the jam-subsequent paper sheet may be possibly jammed in midcourse of applying the pre-purge processing thereto.
In this connection, in an image forming apparatus for production printing use, which has been increasingly proliferated in the market of the high-speed mass-production printing (image forming operation) in recent years, a plurality of paper sheet feeding apparatuses may be coupled to the image forming apparatus concerned, and as a result, the length of the conveyance path is liable to become longer than ever. In this case, when the jam-subsequent paper sheet has further jammed in the vicinity of a toner image transferring point in midcourse of applying the pre-purge processing thereto, none of an ejecting path or a tray is provided for conveying and ejecting another jam-subsequent paper sheet, remaining at a position upstream therefrom, in the vicinity of the paper sheet feeding section or the image forming section.
In other words, arisen is a new problem that it becomes difficult for the image forming apparatus of production printing use to cope with a certain abnormality generated in the jam-subsequent paper sheet in midcourse of applying the pre-purge processing thereto. However, none of Documents 1 through 5 set forth a technology for providing a countermeasure to cope with the above-mentioned problem, and so far, it has been impossible to eject the jam-subsequent paper sheet effectively.